Biz & IT —

Google to strip Chrome of SSL revocation checking

Comparing online revocation checking to seat belts that snap when you crash, a …

Google's Chrome browser will stop relying on a decades-old method for ensuring secure sockets layer certificates are valid after one of the company's top engineers compared it to seat belts that break when they are needed most.

The browser will stop querying CRL, or certificate revocation lists, and databases that rely on OCSP, or online certificate status protocol, Google researcher Adam Langley said in a blog post published on Sunday. He said the services, which browsers are supposed to query before trusting a credential for an SSL-protected address, don't make end users safer because Chrome and most other browsers establish the connection even when the services aren't able to ensure a certificate hasn't been tampered with.

"So soft-fail revocation checks are like a seat-belt that snaps when you crash," Langley wrote. "Even though it works 99% of the time, it's worthless because it only works when you don't need it."

SSL critics have long complained that the revocation checks are mostly useless. Attackers who have the ability to spoof the websites and certificates of Gmail and other trusted websites typically have the ability to replace warnings that the credential is no longer valid with a response that says the server is temporarily down. Indeed, Moxie Marlinspike's SSL Strip hacking tool automatically supplies such messages, effectively bypassing the measure.

"While the benefits of online revocation checking are hard to find, the costs are clear: online revocation checks are slow and compromise privacy," Langley added. That's because the checks add a median time of 300 milliseconds and a mean of almost 1 second to page loads, making many websites reluctant to use SSL. Marlinspike and others have also complained that the services allow certificate authorities to compile logs of user IP addresses and the sites they visit over time.

Chrome will instead rely on its automatic update mechanism to maintain a list of certificates that have been revoked for security reasons. Langley called on certificate authorities to provide a list of revoked certificates that Google bots can automatically fetch. The time frame for the Chrome changes to go into effect are "on the order of months," a Google spokesman said.